Basis for original (SCP) IDLH: From the data given by ACGIH [1971], it does not appear that exposure to a high concentration of yttrium could impede escape within 30 minutes. For this draft technical standard, therefore, respirators have been selected on the basis of the assigned protection factor afforded by each device up to 500 ´ the OSHA PEL of 1 mg Y/m3 (i.e., 500 mg Y/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 500 mg Y/m3.

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

Lethal dose data:

Species

Reference

Route

LD50(mg/kg)

LDLo(mg/kg)

Adjusted LD

Derived value

Y2O3 Rat

Spassky 1978

oral

—–

>10,000

>55,300 mg Y/m3

>5,530 mg Y/m3

Y2O3 Mouse

Spassky 1978

oral

—–

> 6,000

>33,180 mg Y/m3

>3,318 mg Y/m3

Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 500 mg Y/m3Basis for revised IDLH: The available toxicological data contain no evidence that an acute exposure to a high concentration of yttrium compounds would impede escape or cause any irreversible health effects within 30 minutes. However, the revised IDLH for yttrium compounds is 500 mg Y/m3 based on being 500 times the NIOSH REL and OSHA PEL of 1 mg Y/m3 (500 is an assigned protection factor for respirators and was used arbitrarily during the Standards Completion Program for deciding when the “most protective” respirators should be used for particulates).